UV bulbs are designed for the Royal Sovereign UV Counterfeit Detector and Four-Way Counterfeit Detector. The ultraviolet light is used for security thread detection. These 6-watt ultraviolet bulbs are used to check for UV-sensitive strips and help identify fake bills and phony IDs. Most government issued IDs such as drivers licenses will have an invisible holographic image printed on the ID that will only be revealed under UV light. Each bulb lasts approximately 1000 hours.